The invention relates to a diagnostic device for performing solid phase immunoassays to detect the presence of antigens or antibodies in biological or non-biological fluids. The teachings of the invention are incorporated in a bi-directional lateral chromatographic device for use in solid phase immunoassays or for the non-immunological detection or quantitation of proteins or substances in biological or non-biological fluids.
More particularly, the invention relates to devices and methods which utilize filter means for testing biological fluids to detect the presence of analytes such as bacterial, viral, parasitic, or fungal antigens and immunoglobulins, hormones, serum proteins, drugs and the like.
Typical of prior art devices presently in use are the teachings of U.S. Pat. No. 4,623,461, which discloses a filter body located in a housing having an opening therein for the reception of a suspension sample to permit the upper face of the filter to trap colored or particulate matter contained within the specimen and prevent such matter from reaching the bottom face of the reaction zone, which has been previously treated with a suitable reactant. The perimeter of the filter is engaged with a suitable absorbent body and the absorbent body is intended to receive the outward diffusion of liquids applied to the filter.
One of the disadvantages of the '461 construction lies in the fact that the fluid flow from the point of application of the suspension to the absorbent body is unidirectional and a subtantial accumulation of solids at the point of application of the sample suspension is inevitable, which will seriously impinge upon the resultant chromatological or other type of test reading imparted by the device.
U.S. Pat. No. 3,825,410 discloses a disposable combined storage and reaction cell for use in the performance of chemical and biological reactions which receives reactants dispensed therein and maintains the same in stored condition so that they remain stable. Reactants will not mutually react until such time as it is required to initiate the reaction.
The immobilization of the reactants is accomplished by such procedures as freeze drying and the reaction is initiated by the introduction of a sample to be analyzed, whereafter separation of bound and free ligand can be performed either within the unit itself or externally.
The reaction cell of the '410 patent may include a filter so that the entire process of separation can be completed within the reaction cell and the filter be removed from the reaction cell and submitted for radioactivity or other tracer counts.
U.S. Pat. No. 3,888,629 discloses a reaction cell for performing various types of assays which incorporates a matrix pad of absorbent material retaining the necessary reagents for the reaction and serving as a site in which the reaction totally occurs. A separable lower chamber incorporates absorbent material abutting the matrix pad to promote filtration through the pad after the reaction has taken place.
Both patents are characterized by the mere utilization of the filter as a pass-through device which is time-consuming and which is hindered by the deposition of solids out of the suspension sample.